Generally, all the network box cameras have correct back focal length, so that users can choose different C/CS mount lenses for diversity video surveillance applications. Commonly, it's not necessary to adjust camera's back focal length. In real installation and usage, camera may not obtain clear images although adjusting zoom & focus rods to threshold value. At this point installers need to adjust the camera back focal length.
Back focus refers to the "focal flange length". This is the distance between the rear lens element and the image sensor (CCD/CMOS). Back focus is only applicable to cameras (i.e. network box camera) with detachable lenses, consumer-level cameras don't support back focus adjustment.
Manually adjust the back focus length, procedures as below:
To Auto-Iris lens, the adjustment method is different. During bright sunlight, the lens iris is closed and the depth of field (FoV) very wide. When the light level drops, the lens iris opens and the depth of field decreases. To obtain the optimum focus, the network camera should be back focused with the len's iris fully opened. Proper back-focus adjustment also holds true for zoom lenses which need to be properly adjusted to hold focus through the zoom range. Back focus adjustment ensures that the network camera's image keeps in focus during changing lighting conditions. This is a common problem in security camera installation where one sees a sharp image during daytime but a blur at night.
Steps to adjust back focus for auto-iris lens security camera.
Note: When adjusting the zoom, it will be necessary to re-adjust the focus. However, the CS mount ring locking screw must not be loosened.
With the continuous development of technology, network cameras are able to provide much higher resolution, and offer high definition video surveillance experience. Meanwhile, this also brings a great difficulty to installer. The conventional manual back focal length technology no longer meet the needs of high definition video surveillance.
With purpose to simplify the installation of network box camera, some security camera manufacturers (Hikvision, Bosch, Dahua, Panasonic, Sony, Cisco, Samsung) launched network cameras with auto back focus function. Auto back focus feature enables camera to adjust back focal length automatically.
Currently, there are two different designs for auto back focus:
The Auto Back Focus (ABF) makes network camera easy for an installer to accurately focus the camera for both day and night operation. The wizard is activated from the web browser or from the on-board camera push button making it easy to choose the workflow that suits best. The automatic motorized back focus adjustment with 1:1 pixel mapping ensures the camera is always focused accurately.
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